simplifying committing of changed versioned files

scripts/bump_version

@@ -1,6 +1,8 @@
 #!/bin/bash
 
 main() {
+  set -euo pipefail  # Bash safemode
+
   local version=$1
   if [[ -z "${version}" ]]; then
     echo "USAGE: $0 1.3.2"
@@ -15,7 +17,7 @@ main() {
 
   git checkout -b version-${version}
   # Commit the new version
-  git commit setup.py moto/__init__.py -m "bumping to version ${version}"
+  git commit -a -m "bumping to version ${version}"
   # Commit an updated IMPLEMENTATION_COVERAGE.md
   make implementation_coverage || true
   # Open a PR